Prop Question

[rivergames]

On my fishing boat, The recommended prop is a 15-1/2"D x 17"P

My local shop has a 15-1/4"D x 17"P.

What would that 1/4" smaller Diameter do to the handing of the boat?

 

[Nanu/Nanu]

Do you really want to know?

My wife says 1/4" makes a big difference.

 

[LargeOrangeFont]

Less load on the engine the boat will probably run slightly higher RPM.

Going to a bigger diameter prop felt like I put a slightly taller final drive on my car. It cruised at the same speed at a lower RPM.

So I would believe going slightly smaller would to the opposite, and also slightly numb the handling/response of the boat, because your blades are a little smaller.

 

[FreeBird236]

On my fishing boat, The recommended prop is a 15-1/2"D x 17"P

My local shop has a 15-1/4"D x 17"P.

What would that 1/4" smaller Diameter do to the handing of the boat?

Not an expert, but I think it will raise the RPM a little at any given speed, like going to a slightly lower pitch. Don't know if it would be equal to a full 1" step.

 

[LuckyStrike]

On my fishing boat, The recommended prop is a 15-1/2"D x 17"P

My local shop has a 15-1/4"D x 17"P.

What would that 1/4" smaller Diameter do to the handing of the boat?

Little higher rpm not enough to make a difference IMO


Sent from my iPhone using Tapatalk

 

[Trash]

Can't really answer the question with the information given UNLESS the two props are the same make and model, which they likely are not. Pitch has the biggest affect on rpm. Diameter much less so. The biggest wild card here is blade style and surface area of each blade.

IF the two props were identical (say both were Mirage 3 blades) you would be fine running the prop with 1/4" less diameter. Realistically this is not the case here. Pictures of both props and more details would help.

You would not be able to directly compare say a Laser II 17" pitch and a Rev 4 in 17" pitch. Totally different in blade count, diameter, and blade loading/surface area etc. in spite of having the same pitch.

 

[rivergames]

Can't really answer the question with the information given UNLESS the two props are the same make and model, which they likely are not. Pitch has the biggest affect on rpm. Diameter much less so. The biggest wild card here is blade style and surface area of each blade.

IF the two props were identical (say both were Mirage 3 blades) you would be fine running the prop with 1/4" less diameter. Realistically this is not the case here. Pictures of both props and more details would help.

You would not be able to directly compare say a Laser II 17" pitch and a Rev 4 in 17" pitch. Totally different in blade count, diameter, and blade loading/surface area etc. in spite of having the same pitch.

Yamaha Salt Water Series

 

[HBCraig]

I cut my Bravo down 1/2" diameter. From what the prop guy said, the smaller diameter gets out of the hole a bit better.

 

[Trash]

I'm not seeing the Yamaha Saltwater series in two different diameters with the same pitch. Yamaha, like others typically alter diameter when pitch changes.

IF its the same exact prop (blades, pitch etc) except the diameter my bet is you would be fine with a 1/4" smaller diameter.